Display device

ABSTRACT

A display device includes a multilayer passivation structure and has an undercut formed in the passivation structure such that a connection between a cathode and an auxiliary wiring is formed inside the undercut, so as to prevent voltage drop of the cathode and influence of hydrogen on thin film transistors and thus to improve reliability of the display device.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No.10-2020-0120896, filed on Sep. 18, 2020, which is hereby incorporated byreference in its entirety as if fully set forth herein.

BACKGROUND Field of the Disclosure

The present disclosure relates to a display device, and moreparticularly, to a display device which uses a reflective electrode asan anode so as to exhibit high reflectance, secures connection betweenan auxiliary wiring and a cathode in a passivation structure, andprevents hydrogen from penetrating into thin film transistors

Description of the Background

As society has recently entered the information age, the field ofdisplays for visually displaying electrical information signals hasrapidly developed and, in order to satisfy such development, variousdisplay devices having excellent performance, such as slimness, lightweight and low power consumption, have been developed and have rapidlyreplaced conventional cathode ray tubes (CRTs).

Among self-light emitting display devices, which do not require separatelight sources, achieve compactness and clear color display and includelight emitting devices within a display panel, are considered ascompetitive applications.

In light emitting devices provided in respective subpixels of a displaydevice, because one electrode is integrally provided throughout theentirety of an active area of the display device, the electrodeintegrally provided throughout the subpixels is formed to have a largesize. In such a large-sized electrode, auxiliary connection parts,configured to prevent voltage drop in a region far away from a region towhich voltage is applied, are required.

SUMMARY

Accordingly, the present disclosure is directed to a display device,which includes auxiliary connection parts in a passivation structure soas to prevent voltage drop of a cathode and penetration of hydrogen,that substantially obviates one or more problems due to limitations anddisadvantages of the related art.

The present disclosure is to provide a display device which includes anundercut provided in a multilayer passivation structure, and forms aconnection between a cathode and an auxiliary wiring at the undercut inthe passivation structure, so as to prevent voltage drop of the cathodeand to improve reliability. Here, the passivation structure includes aplurality of layers formed of inorganic insulating films includingdifferent components, and may thus prevent hydrogen generated from anencapsulation film formed thereon through a low-temperature process frompenetrating into elements provided under the passivation structure.

Additional advantages and features of the disclosure will be set forthin part in the description which follows and in part will becomeapparent to those having ordinary skill in the art upon examination ofthe following or may be learned from practice of the disclosure. Otheradvantages of the disclosure may be realized and attained by thestructure particularly pointed out in the written description and claimshereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the disclosure, as embodied and broadly described herein, a displaydevice includes auxiliary wirings on a substrate, a passivationstructure formed by stacking a first layer and a second layer on theauxiliary wirings and configured such that an open region of the firstlayer is greater in size than an open region of the second layer withrespect to each of the auxiliary wirings, a bank provided on thepassivation structure and configured to have first holes correspondingto the auxiliary wirings and having a greater size than the open regionof the first layer, and second holes corresponding to the emissionparts, and light emitting devices respectively provided in the emissionparts, each of the light emitting devices including a first electrodeincluding a reflective metal layer, an organic layer including at leastone emission layer, and a second electrode, wherein the second electrodeextends towards the auxiliary wiring inside each of the second holes ofthe bank and is directly connected to the auxiliary wiring in the openregion of the first layer under the second layer.

In another aspect of the present disclosure, a display device includes asubstrate having emission parts, transmission parts and auxiliaryconnection parts, auxiliary wirings provided in the auxiliary connectionparts of the substrate, a passivation structure formed by stacking afirst layer and a second layer on the auxiliary wirings and configuredsuch that an open region of the first layer is greater in size than anopen region of the second layer with respect to each of the auxiliarywirings, a bank provided on the passivation structure and configured tohave first holes corresponding to the auxiliary wirings and having agreater size than the open region of the first layer, second holescorresponding to the emission parts, and third holes corresponding tothe transmission parts, and light emitting devices respectively providedin the emission parts, each of the light emitting devices including afirst electrode including a reflective metal layer, an organic layerincluding at least one emission layer, and a second electrode, whereinthe second electrode extends towards the auxiliary wiring in the openregion of the first layer under the second layer.

It is to be understood that both the foregoing general description andthe following detailed description of the present disclosure areexemplary and explanatory and are intended to provide furtherexplanation of the disclosure as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this application, illustrate aspect(s) of the disclosure andtogether with the description serve to explain the principle of thedisclosure.

In the drawings:

FIG. 1 is a plan view illustrating a display device according to oneaspect of the present disclosure;

FIG. 2 is a longitudinal-sectional view taken along line I-I′ of FIG. 1;

FIG. 3 is a longitudinal-sectional view of region A of FIG. 1, takenalong line II-II′ of FIG. 1;

FIGS. 4A to 4F are longitudinal-sectional views illustrating a methodfor manufacturing the display device according to one aspect of thepresent disclosure;

FIG. 5A is an SEM image of a display device to which an undercutstructure according to Test Example 1 is applied;

FIG. 5B is a photograph representing mura occurring on the surface of adisplay device to which a single passivation film according to TestExample 2 is applied;

FIG. 6 is a graph representing negative bias thermal stress (NBTS)characteristics at a high temperature of the display device according toTest Example 2 and a display device according to Test Example 3;

FIG. 7 is a longitudinal-sectional view illustrating the evaluatedstructure of an undercut of a multilayer passivation structure accordingto Test Example 4;

FIG. 8 is an SEM image representing the multilayer passivation structureaccording to Test Example 4 shown in FIG. 7 after dry etching;

FIG. 9 is a longitudinal-sectional view illustrating a display deviceaccording to another aspect of the present disclosure;

FIGS. 10A to 10F are longitudinal-sectional views illustrating a methodfor manufacturing the display device according to another aspect of thepresent disclosure; and

FIG. 11 is an SEM image of an undercut structure according to TestExample 5 (i.e., the undercut structure of the display device) accordingto the present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to the exemplary aspects of thepresent disclosure, examples of which are illustrated in theaccompanying drawings. In the following description of the aspects andthe drawings, the same or similar elements are denoted by the samereference numerals throughout the specification. In the followingdescription of the aspects of the present disclosure, a detaileddescription of known functions and configurations incorporated hereinwill be omitted when it can make the subject matter of the presentdisclosure rather unclear. Further, the names of elements used in thefollowing description of the aspects of the present disclosure areselected in consideration of ease of preparation of the specification,and can thus differ from the names of parts of an actual product.

The shapes, sizes, ratios, angles and numbers of elements given in thedrawings to describe the aspects of the present disclosure are merelyexemplary, and thus, the present disclosure is not limited to theillustrated details. In the following description of the aspects, theterms “including”, “comprising” and “having” are to be interpreted asindicating the presence of one or more other characteristics, numbers,steps, operations, elements or parts stated in the specification orcombinations thereof, and do not exclude the presence of othercharacteristics, numbers, steps, operations, elements, parts orcombinations thereof, or the possibility of adding the same, unless theterm “only” is used. It will be understood that a singular expression ofan element(s) encompasses a plural expression unless stated otherwise.

In the interpretation of elements included in the various aspects of thepresent disclosure, it is to be interpreted that the elements includeerror ranges unless stated otherwise.

In the following description of the aspects, it will be understood that,when positional relationships are expressed, for example, when anelement is said to be “on”, “above”, “under” or “beside” anotherelement, the two elements can directly contact each other, or one ormore other elements can be interposed between the two elements, unlessthe term “just” or “directly” is used.

In the following description of the aspects, it will be understood that,when temporal relationships are expressed, for example, when termsexpressing a sequence of events, such as “after”, “subsequent to”,“next” and “before” are used, the terms encompass both a continuousrelationship between the events and a discontinuous relationship betweenthe events, unless the term “just” or “directly” is used.

In the following description of the aspects, it will be understood that,when the terms “first”, “second”, etc. are used to describe variouselements, these terms are used merely to distinguish the same or similarelements. Therefore, a first element described hereinafter could betermed a second element without departing from the technical scope ofthe disclosure.

Respective features of the various aspects of the present disclosure canbe partially or wholly coupled to or combined with each other and beinterlocked or driven in various technical manners, and the respectiveaspects can be implemented independently of each other or be implementedtogether through connection therebetween.

Hereinafter, a display device according to the present disclosure willbe described with reference to the accompanying drawings.

FIG. 1 is a plan view illustrating a display device according to oneaspect of the present disclosure. Further, FIG. 2 is alongitudinal-sectional view taken along line I-I′ of FIG. 1, and FIG. 3is a longitudinal-sectional view of region A of FIG. 1, taken along lineII-II′ of FIG. 1.

As shown in FIGS. 1 to 3, the display device according to one aspect ofthe present disclosure includes auxiliary wirings 130 on a substrate100, a passivation structure 1400 formed by stacking a first layer 140and a second layer 150 on the auxiliary wirings 130 and having anundercut UC with respect to each of extensions 130 a of the auxiliarywirings 130, a bank 170 configured to have first holes 170H1 greater insize than an open region 140H of the first layer 140 of the passivationstructure 1400 including the undercut UC, and light emitting devicesOLED respectively provided in emission parts E.

In the display device according to the present disclosure, the lightemitting device OLED includes a first electrode 145 including areflective metal layer 1412, an organic layer 180 including at least oneemission layer, and a second electrode 190. The second electrode 190 isa transparent electrode so that emitted light passes through the secondelectrode 190.

The extension 130 a of the auxiliary wiring 130 is integrated with theauxiliary wiring 130 such that ground voltage or VSS voltage having aregular voltage value applied to the auxiliary wiring 130 is alsoapplied to the extension 130 a, and is conductively connected to thesecond electrode 190 so as to transmit the voltage to the secondelectrode 190. The extension 130 a of the auxiliary wiring 130 ispatterned in a specific region and is thus referred to as an auxiliaryelectrode, or receives the same VSS voltage as the auxiliary wiring 130and is thus considered as being equivalent to the auxiliary wiring 130.In some cases, an auxiliary connection part connected to the secondconnection 190 may be directly formed on the auxiliary wiring 130without the extension 130 a of the auxiliary wiring 130.

In the display device according to the present disclosure, a region inwhich the extension 130 a of the auxiliary wiring 130 and the secondelectrode 190 are connected to each other is disposed every one or morepixels. Through connection between the extension 130 a of the auxiliarywiring 130 and the second electrode 190, even though the secondelectrode 190 is integrally formed throughout a large area in the activearea AA, VSS voltage is uniformly applied to the second electrode 190without deviations among regions. In this case, one pixel may include aplurality of emission parts E and one transmission part T or a pluralityof transmission parts T. The auxiliary wiring 130 may be disposed in afirst direction in each region including a plurality of emission parts Eand at least one transmission part T, and the extension 130 a of theauxiliary wiring 130 may be disposed in a second direction every two ormore emission parts E or every one or more transmission parts T.

FIG. 1 illustrates that the extension 130 a of the auxiliary wiring 130is disposed between the transmission parts T and is connected to thesecond electrode 190. However, the disclosure is not limited thereto,and the extension 130 a of the auxiliary wiring 130 may be disposedbetween the emission part E and the transmission part T and, in somecases, may be disposed between the emission parts E. The extensions 130a are desirably provided in regions adjacent to the auxiliary wirings130 on the grounds of reducing line resistance. FIG. 1 illustrates astructure in which the extension 130 a of the auxiliary wiring 130 isprovided adjacent to one transmission part T and, in order to preventinfluence on the emission parts E due to disconnection of the organiclayer 180 at the undercut UC in the passivation structure 1400 on theextension 130 a of the auxiliary wiring 130, the extension 130 a isprovided so as to be spaced apart from the emission parts E, anauxiliary wiring connection part is provided on the extension 130 a ofthe auxiliary wiring 130.

In the display device according to the present disclosure, thepassivation structure 1400, which is provided so as to protect thin filmtransistors, may not only perform connection between the auxiliarywiring 130 provided under the passivation structure 1400 and the secondelectrode 190 provided on the passivation structure 1400 through theundercut UC but also prevent hydrogen from penetrating or diffusing intothe thin film transistors under the passivation structure 1400, therebybeing capable of preventing changes in the characteristics of the thinfilm transistors. Therefore, the passivation structure 1400 according tothe present disclosure includes at least two layers, and covers wirings,such as gate lines and data lines, except for the extension 130 a of theauxiliary wiring 130 around the undercut UC, and the thin filmtransistors.

The passivation structure 1400 includes a stack of the first layer 140and the second layer 150, and the first open region 140H of the firstlayer 140 is greater in size than a second open region 150H of thesecond layer 150 in at least one side thereof with respect to theextension 130 a of the auxiliary wiring 130. FIG. 1 illustrates that thefirst open region 140H has a greater width than the second open region150H having a rectangular shape at three sides thereof, and the undercutUC is formed at these three sides. However, the disclosure is notlimited thereto, and when the second open region 150H has otherpolygonal shapes than the rectangular shape, the first open region 140Hmay protrude more than the remaining sides of the second open region150H except for one side of the second open region 150H. Here, thereason why one side of the second open region 150H is located fartheroutwards than the first open region 140H is that the undercut is notformed at this region. When the first open region 140H is greater insize than the second open region 150H at all sides thereof, the undercutis formed at all sides of the second open region 150H, and in this case,the second electrode 190 located at the side part of the second layer150 and the second electrode 190 located on the extension 130 a of theauxiliary wiring 130 are separated from each other and thus the signalof the auxiliary wiring 130 is not capable of being applied to thesecond electrode 190. Therefore, when the second open region 150H has apolygonal shape having n sides, the first open region 140H is set to begreater in size than the second open region 150H at 1 to n−1 sidesthereof so that the undercut UC is formed at regions having a sizedifference between the first and second open regions 140H and 150H, andthe first open region 140H is set to be not greater in size than thesecond open region 150H at the remaining sides thereof. Thereby, thesecond electrode 190 goes down from the upper part of the second layer150 along the side parts of the second layer 150 and the first layer 140and is formed evenly on the extension 130 a of the auxiliary wiring 130,as shown in the right region of FIG. 3, and the second electrode 190extends so as to be closer to the first layer 140 in the undercut regionthan the organic layer 180, and is thus directly connected to theextension 130 a of the auxiliary wiring 130, as shown in the left regionof FIG. 3.

In contrast to the example shown in FIG. 1, as another example, when thesecond open region 150H has a hexagonal shape, the first open region140H may protrude more than the remaining five sides of the second openregion 150H except for one side of the second open region 150H, or thefirst open region 140H may protrude more than four sides, three sides,two sides, or one side of the second open region 150H. An undercut UC isdefined in regions in which the first open region 140H protrudes morethan the second open region 150H, and thus, as shown in FIG. 3, thesecond layer 150 of the passivation structure 1400 is located fartherinto the first hole 170H of the bank 170 than the first layer 140.Further, the region in which the first layer 140 is removed more thanthe second layer 150 is defined as the undercut.

In the region in which the first open region 140H of the first layer 140protrudes more than the second open region 150H of the second layer 150,the protruding width of the first open region 140H may be 0.4 μm to 2.0μm. When the protruding width of the first open region 140H is smallerthan 0.4 μm in the region in which the first open region 140H protrudes,it may be difficult to secure the undercut region sufficient for thesecond electrode 190 to be connected to the extension 130 a of theauxiliary wiring 130, and when the protruding width of the first openregion 140H exceeds 2.0 μm in the region in which the first open region140H protrudes, the second layer 150 may collapse in subsequentprocesses.

FIG. 1, which is a plan view of the display device according to oneaspect of the present disclosure, illustrates a part of the active areaAA in which display is realized. A plurality of emission parts E and aplurality of transmission parts T are disposed in the active area AA.Each of the emission parts E emits light with a designated color, andthe transmission parts T transmit light from below. The bank 170 isprovided so as to expose the emission parts E and the transmission partsT. Further, the bank 170 covers the auxiliary wirings 130 except for theextensions 130 a connected to the second electrodes 190. That is, thebank 170 has the first holes 170H1 corresponding to the extensions 130a, second holes 170H2 corresponding to the emission parts E, and thirdholes 170H3 corresponding to the transmission parts T.

An organic insulating film 160 may be disposed between the bank 170 andthe passivation structure 1400, and the organic insulating film 160 maycover steps of the surface of the passivation structure 1400 so as toplanarize the surface of the passivation structure 1400. The organicinsulating film 160 may be referred to as an overcoat layer or aplanarization layer in terms of functions thereof. In some cases, theorganic insulting film 160 may be omitted.

The first and second open regions 140H and 150H of the first and secondlayers 140 and 150 of the passivation structure 1400 are located on theextension 130 a of the auxiliary wiring 130. The first and second openregions 140H and 150H of the passivation structure 1400 are locatedinside a hole 160H of the organic insulating film 160 and the first hole170H1 of the bank 170, parts of the first and second layers 140 and 150of the passivation structure 1400 are located inside the hole 160H ofthe organic insulating film 160 and the first hole 170H1 of the bank 170and cover a part of the extension 130 a of the auxiliary wiring 130, andthe undercut is defined such that the first open region 140H of thefirst layer 140 is greater in size than the second open region 150H ofthe second layer 150. The first layer 140 has the undercut UC withrespect to the second layer 150, and the second electrode 190 isconnected to the extension 130 a of the auxiliary wiring 130 in thefirst open region 140H which is greater in size than the second openregion 150H.

The passivation structures 1400 may include only inorganic insulatingfilms, and the first layer 140 contacting at least the extension 130 aof the auxiliary wiring 130 and the second layer 150 contacting thefirst layer 140 have different etching properties. Therefore, the firstand second open regions of the first and second layers 140 and 150 ofthe passivation structure 1400 are primarily formed to have the samewidth or similar widths, and then, the first layer 140 is secondarilyfurther etched compared to the second layer 150 so that the first openregion 140H is greater in size than the second region 150H. Here, a partof the first open region 140H of the first layer 140 which is removedmore than the second open region 150H of the second layer 150 may bedefined as the undercut UC.

In the display device according to the present disclosure, because thepart of the first open region 140H of the first layer 140 which isremoved more than the second open region 150H of the second layer 150 isdefined as the undercut UC, the thickness of the first layer 140 is setto be equal to or greater than the sum of the thickness of the organiclayer 180 and the thickness of the second electrode 190, and thus, whenthe organic layer 180 is deposited, the organic layer 180 accumulated inthe open region 150H of the second layer 150 in the undercut region doesnot close the side part of the undercut UC. That is, the organic layer180 having straightness is deposited on the extension 130 a of theauxiliary wiring 130 exposed outside the undercut UC, and is thusaccumulated in the second open region 150H of the second layer 150. Whenthe organic layer 180 is deposited, even though the organic layer 180 isaccumulated on the extension 130 a of the auxiliary wiring 130corresponding to a part of the undercut region due to partial shadowing,the thickness of the organic layer 180 in the undercut region is lessthan the thickness of the organic layer 180 accumulated in the flat partof the second open region 150H. Further, because the organic layer 180has poor step coverage even in a shaded part, the organic layer 180 maybe discontinuous in the undercut region, and a metal material formingthe second electrode 190 deposited on the organic layer 180 hasexcellent step coverage compared to the organic layer 180, enters intothe undercut UC while covering the upper and side parts of the organiclayer 180, and is directly connected to the extension 130 a of theauxiliary wiring 130.

The first layer 140 and the second layer 150 may be different inorganicinsulating films, and for example, the first layer 140 may be an oxidefilm, such as a silicon oxide (SiO_(x)) film or an aluminum oxide(Al₂O₃) film, and the second layer 150 may be a nitride film, such as asilicon nitride (SiN_(x)) film. As another example, the first layer 140may be a silicon nitride (SiN_(x)) film, and the first layer 150 may bea silicon oxide (SiO_(x)) film or an aluminum oxide (Al₂O₃) film. Insome cases, one of the first layer 140 and the second layer 150 may bean oxide film or a nitride film, and the other may be an oxynitridefilm, such as silicon oxynitride (SiON_(x)). In addition to theabove-described examples, the first layer 140 and the second layer 150may be inorganic insulating films having different composition ratios ofoxygen and nitrogen so as to react to different etchants or etchinggases, and thereby, the first open region 140H and the second openregion 150H may have different areas.

In the display device according to the present disclosure, because thepart of the first open region 140H of the first layer 140 which isremoved more than the second open region 150H of the second layer 150 isdefined as the undercut UC, in order to stably connect the secondelectrode 190 to the extension 130 a of the auxiliary wiring 130, thefirst layer 140 may be formed to have a thickness which is equal to orgreater than the sum of the thickness of the organic layer 180 and thethickness of the second electrode 190. Each or any one of the firstlayer 140 and the second layer 150 may include a plurality of filmsformed of the same material. Alternatively, each or any one of the firstlayer 140 and the second layer 150 may include a plurality of filmsformed of materials having the same etching properties.

The first layer 140 may include a plurality of inorganic insulatingfilms formed of the same component so as to correspond to the thicknessof the undercut UC.

The passivation structure 1400 of the display device according to thepresent disclosure includes the first layer 140 and the second layer 150having different composition ratios of oxygen and nitrogen, and thusexhibits an excellent function of preventing penetration of hydrogenfrom above the light emitting devices OLED compared to a singlepassivation film. Particularly, a film forming process may be performedat a high temperature exceeding 200° C., before formation of the organiclayer 180. Therefore, the first and second layers 140 and 150 of thepassivation structure 1400 may have high density, and may thus blockdownward migration of hydrogen and prevent changes in characteristics ofthe semiconductor layer of the thin film transistors. For example, incase of a thin film transistor including an oxide semiconductor layer,change in threshold voltage is greatly influenced by a hydrogen content,and therefore, in the display device according to the presentdisclosure, the passivation structure 140 configured to protect the thinfilm transistors includes a plurality of films formed of differentmaterials having different composition ratios of oxygen and nitrogen,thereby being capable of strengthening the function of protecting thethin film transistors.

An encapsulation layer structure 300 may be formed so as to protect thelight emitting devices OLED.

Because the organic layer 180 is easily denatured by heat and opticalcharacteristics of the organic layer 180 are changed by heat, the secondelectrode 190 and the encapsulation layer structure 300 formed afterformation of the organic layer 180 must be manufactured at alow-temperature lower than 200° C., particularly equal to or lower than110° C., and more particularly equal to or lower than 80° C. Therefore,even though the encapsulation layer structure 300 includes inorganicencapsulation layers 310 and 330 for preventing moisture penetration,the film formation process of the encapsulation layer structure 300 isperformed at a low temperature, and thus, densities of films used as theinorganic encapsulation layers 310 and 330 are low and hydrogen includedin the inorganic encapsulation layers 310 and 330 easily migratesdownwards. The passivation structure 1400 configured to protect the thinfilm transistors of the display device according to the presentdisclosure has relatively high density, thus being capable of preventingmigration of hydrogen included in the inorganic encapsulation layers 310and 330 and blocking diffusion of hydrogen into the thin filmtransistors provided under the passivation structure 1400. In this case,even though the inorganic encapsulation layers 310 and 330 are formed ofa silicon nitride (SiN_(x)) film or a silicon oxynitride (SiON_(x))film, the inorganic encapsulation layers 310 and 330 are formed by thelow-temperature process, and thus, the densities of the inorganicencapsulation layers 310 and 330 are lower than the density of a siliconnitride (SiN_(x)) film or a silicon oxynitride (SiON_(x)) film includedin the first layer 140 and/or the second layer 150 of the passivationstructure 140, which is located below the organic layer 180 and may thusbe formed by the high-temperature process. Therefore, the passivationstructure 1400 may block diffusion of hydrogen from the inorganicencapsulation layers 310 and 330.

The auxiliary wiring 130 provided below the bank 170 is connected to thesecond electrode 190 of the light emitting device OLED provided in theemission part E through the extension 130 a of the auxiliary wiring 130,thereby being capable of preventing voltage drop of the second electrode190 and allowing the second electrode 190 to have uniform voltagethroughout the entirety of the second electrode 190.

The auxiliary wiring 130 has the extensions 130 a provided at one sidethereof so as to be adjacent to corresponding transmission parts T, asshown in FIG. 1, and may thus have connections with the secondelectrodes 120. Here, the bank 170 may have the first holes 170H1corresponding to the extensions 130 a, the second holes 170H2corresponding to the emission parts E, and the third holes 170H3corresponding to the transmission parts T.

The light emitting device OLED is provided in each of the emission partsE, and the light emitting device OLED includes the first electrode 145which is patterned, the organic layer 180 and the second electrode 190,which are sequentially stacked. The first electrode 145 is provided ineach of the emission parts E so as to have a slightly larger size thanthe emission part E, and one side of the first electrode 145 may extendso as to form a first connection part CT1 connected to the thin filmtransistor provided below the light emitting device OLED. The part ofthe first electrode 145 extending from the size of the emission part Emay overlap the bank 170, and may thus be shielded by the bank 170. Theemission part E is defined by the second hole 170H2 of the bank 170opposite the first electrode 145, and the first electrode 145, theorganic layer 180 and the second electrode 190, which are verticallystacked in the emission part E, function as the light emitting deviceOLED.

In the display device according to the present disclosure, the organiclayer 180 and the second electrode 190 may be formed on the substrate100 without using a fine metal mask (FMM). Here, the passivationstructure 1400 protecting the thin film transistors includes a pluralityof layers, the undercut structure UC, in which the first open region140H of the first layer 140 of the passivation structure 1400 is greaterin size than the second open region 150H of the second layer 150, isprovided so as to correspond to the extension 130 a of the auxiliarywiring 130, and the organic layer 180 is disconnected at the undercutstructure UC. Further, the second electrode 190 formed on the organiclayer 180 has excellent step coverage compared to the organic layer 180,enters into the undercut structure UC, and is directly connected to theextension 130 a of the auxiliary wiring 130. Therefore, the secondelectrode 190 may be connected to the extension 130 a of the auxiliarywiring 130 without a fine metal mask configured to pattern the organiclayer 180 and the second pattern 190. This is because the organic layer180 and the second electrode 190 formed after formation of the undercutstructure UC of the passivation structure 1400 have different depositioncharacteristics due to the organic material and the electrode materialthereof. The second electrode 190 including the electrode material hasrelatively excellent step coverage.

The edge of the first electrode 145 of the light emitting device OLEDmay be covered with the bank 170 so as to be protected thereby, and theupper part of the first electrode 145 may be protected by theencapsulation layer structure 300 formed after formation of the organiclayer 180 and the second electrode 190. The encapsulation layerstructure 300 may include at least one organic encapsulation layer 320and the inorganic encapsulation layers 310 and 330, which are stackedalternately with the organic encapsulation layer 320. The inorganicencapsulation layers 310 and 330, which prevent penetration of externalmoisture or ambient air, are formed to have a thickness sufficient toprevent the flow of particles generated from the inside of the displaydevice, and prevent influence of the particles on the elements providedunder the encapsulation layer structure 300. All the elements of theencapsulation layer structure 300 may be formed through alow-temperature process.

In the display device according to the present disclosure, the firstelectrode 145 of the light emitting device OLED may include thereflective metal layer 1412, and particularly, when the reflective metallayer 1412 includes a metal or a metal alloy having high reflectance,such as silver (Ag), a silver alloy, or Ag—Pd—Cu (APC), the reflectivemetal layer 1412 reflects light, traveling from the organic layer 180towards the first electrode 145, upwards so as to exit, thereby beingcapable of improving luminous efficacy. In order to maintain stabilityin formation of the reflective metal layer 1412 and interfacial bondingproperties of the reflective metal layer 1412, the first electrode 145may further include a first transparent conductive film 1411 and asecond transparent conductive film 1413 formed of a material, such asindium tin oxide (ITO), on the lower and upper surfaces of thereflective metal layer 1412, as shown in FIG. 2.

Because the display device according to the present disclosure mayinclude the transmission parts T in addition to the emission parts E, asshown in FIG. 1, the organic layer 180 and the second electrode 190 areformed without using a fine metal mask, and may thus be left in thetransmission parts T. Therefore, when the emission parts E are topemission-type emission parts, among the elements of the transmissionparts T configured together with the light emitting devices OLED of theemission parts E, the second electrode 190 may be a transparentelectrode formed of indium tin oxide (ITO) or indium zinc oxide (IZO) inorder to increase transmittance of the transmission parts T. Further,because the area of the emission parts E is reduced when the area of thetransmission parts T is increased, a reflective electrode having higherreflectance is required as the first electrode 145 in order to increasethe luminous efficacy of each of the emission parts E. The displaydevice according to the present disclosure forms the undercut UC throughthe passivation structure 1400 so as to achieve connection between theextension 130 a of the auxiliary wiring 130 and the second electrode190, and thus prevents exposure of the first electrode 145 or a firstelectrode dummy pattern formed in the same layer as the first electrode145 in addition to the emission part E, thereby being capable ofprotecting the first electrode 145, i.e., the reflective electrode,which tends to be oxidized when exposed to the outside.

The organic layer 180 provided in the emission part E includes anemission layer, and the emission layer may be an organic emission layer,an inorganic emission layer including quantum dots, or a hybrid emissionlayer including an organic material and an inorganic material. Inaddition to the emission layer, the organic layer 180 may furtherinclude at least one of a hole injection layer, an auxiliary holetransport layer, a hole transport layer or an electron barrier layer,under the emission layer, and may further include at least one of a holebarrier layer, an electron transport layer or an electron injectionlayer, on the emission layer. In some cases, the organic layer 180 mayinclude a plurality of stacks divided from each other by a chargegeneration layer. In this case, each stack may include a hole transportlayer, an emission layer and an electron transport layer. One or morelayers forming the organic layer 180 may be formed in the active area AAof the substrate 100 without a mask for region division. The active areaAA in which display is substantially realized. At least one of aplurality of layers forming the organic layer 180, for example, theemission layer, may be selectively formed in the emission parts E usinga fine metal mask having openings corresponding to the respectiveemission parts E.

After formation of the bank 170, the organic layer 180 including atleast a hole injection layer, a hole transport layer, an electrontransport layer and an electron injection layer, and the secondelectrode 190 may be formed in common in the active area AA. Some or allof the layers forming the organic layer 180 may not require a fine metalmask (FMM) having fine openings having sizes corresponding to the sizesof the respective emission parts E, and thus, when the organic layer 180and the second electrode 190 are formed without a fine metal mask (FMM),some or all of the layers forming the organic layer 180 may becontinuously formed without disconnection between adjacent emissionparts E and between adjacent emission and transmission parts E and T. Inthis case, because the second electrode 190 is also formed without afine metal mask (FMM) in addition to the organic layer 180, it isdifficult to achieve direct connection between the second electrode 190and the auxiliary wiring 130 due to the presence of the organic layer180 provided under the second electrode 180, and therefore, in thedisplay device according to the present disclosure, the undercut UC isprepared in the passivation structure 1400 located under the first hole170H1 of the bank 170 before formation of the organic layer 180, so thatthe second layer 150 protrudes compared to the first layer 140 havingthe undercut UC, thereby facilitating conductive connection between thesecond electrode 190 and the extension 130 a of the auxiliary wiring130.

That is, in the display device according to the preset disclosure, theundercut UC is defined by protruding the second layer 150 compared tothe first layer 140 of the passivation structure 1400 without changing aseparate deposition mask or using a fine metal mask (FMM), and thesecond electrode 190 enters into the undercut region more than theorganic layer 180 and may thus be directly connected to the extension130 a of the auxiliary wiring 130 while covering the organic layer 180in the undercut region. Here, the organic layer 180 may be formed notonly on the upper parts of the first electrodes 145 of the emissionparts E but also on the upper and side parts of the bank 170, the sidepart of the organic insulating film 160 and the upper surface of thesecond layer 150 exposed from the organic insulating film 160.

A capping layer (not shown) may be further formed on the secondelectrode 190 of the light emitting devices OLED so as to improveextraction of light and to protect the light emitting devices OLED. Whenthe capping layer is further formed, the encapsulation layer structure300 is formed after formation of the capping layer.

In the encapsulation layer structure 300, the first inorganicencapsulation layer 310 located as the lowermost layer may enter intothe undercut UC and thus fill the undercut UC, and in this case,hydrogen generated from the first inorganic encapsulation layer 310 maynot influence the thin film transistors provided in the emission parts Eor non-emission parts through the hydrogen collection function of thefirst layer 140. Further, the auxiliary wirings 130 and the extensions130 a thereof may use a metal having the hydrogen collection function,such as MoTi, thus being capable of improving a function of preventinghydrogen diffusion.

The display device according to the present disclosure includes thetransmission parts T occupying a designated area or more so thatelements on the rear surface of the display device are visible likeglass, and the transmission parts T may transmit light like a kind oftransparent film. When the display device includes the transmissionparts T, the display device may be used as a transparent display device.On the other hand, when the display device according to the presentdisclosure does not include the transmission parts T, the display deviceincludes the first electrode 145 including the reflective metal layer1412 and has the undercut UC in the passivation structure 1400, therebybeing capable of connecting the second electrode 190 to the extension130 a of the auxiliary wiring 130 at the undercut UC in the passivationstructure 1400 while securing reliability of the first electrode 145 andpreventing diffusion of hydrogen into the thin film transistors.

By conductively connecting the first electrode 145 of the light emittingdevice OLED to the thin film transistor TFT, the light emitting deviceOLED may selectively emit light in response to the turning-on/off of thecorresponding thin film transistor. That is, the display deviceaccording to the present disclosure may achieve both light transmissionand light emission through the emission parts E and the transmissionparts T. Here, the emission parts E may include green, white, blue andred emission parts, and a color emission layer configured to selectivelyemit light with a corresponding color may be provided in each emissionpart E, or a color filter layer (not shown) may be provided on theencapsulation layer structure 300 or on an opposite substrate (notshown) so as to implement color display. In the latter case, the lightemitting devices OLED provided in the emission parts E of the respectivesubpixels may emit white light in common, or in some cases, may includecolor emission layers configured to emit light with colors correspondingto the respective color filters thereof in order to improve cavityeffects of light. The emission parts E may include white emission parts,and in this case, the color filter layer may be omitted in the whiteemission parts. When voltage is applied to the thin film transistorsconnected to the emission parts E, the respective emission parts E emitlight with corresponding colors and thus display an image.

In FIGS. 2 and 3, non-described reference numeral 110 indicates a firstinterlayer insulating film, and non-descried reference numeral 120indicates a second interlayer insulating film, and the first and secondinterlayer insulating films 110 and 120 are formed between electrodesforming the thin film transistors or between the electrodes and otherwrings. The first and second interlayer insulating films 110 and 120 maybe silicon oxide films, silicon nitride films or silicon oxynitridefilms.

Hereinafter, a method for manufacturing the display device according toone aspect of the present disclosure will be described with reference tolongitudinal-sectional views taken along line II-II′ of FIG. 1.

FIGS. 4A to 4F are longitudinal-sectional views illustrating the methodfor manufacturing the display device according to one aspect of thepresent disclosure.

In FIGS. 4A and 4G, an illustration of the thin film transistor TFT isomitted, and thus, the thin film transistor TFT shown in FIG. 9 will bereferred to. The auxiliary wiring 130 and the extension 130 a thereofare formed in the same layer as a source electrode and a drain electrodeof the thin film transistor TFT.

As shown in FIG. 4A, a light-shielding layer (with reference to 210, 211and 213 in FIG. 9) is formed on the substrate 100, and then, the firstinterlayer insulating film 110 is formed thereon.

Thereafter, a semiconductor layer (with reference to 214 in FIG. 9) isformed on the first interlayer insulating film 110, and a gateinsulating film (with reference 209 in FIG. 9) and a gate electrode 227are formed in designated regions on the semiconductor layer. Gate lines(not shown) may be formed in the first direction of FIG. 1 in the samelayer as the gate electrode 227.

Thereafter, the second interlayer insulating film 120 is formed so as tocover the gate electrode 227.

Thereafter, the auxiliary wirings 130 and the extensions 130 a of theauxiliary wirings 130 are formed on the second interlayer insulatingfilm 120. The auxiliary wirings 130 and the extensions 130 a thereof mayhave a three-layer structure including a base metal layer 1312 havinghigh conductivity, and first and second functional layers 1311 and 1313provided on the lower and upper surfaces of the base metal layer 1312 soas to have a function of improving interfacial bonding properties and afunction of preventing hydrogen diffusion. Otherwise, the auxiliarywirings 130 and the extensions 130 a thereof may have a two-layerstructure including the base metal layer 1312 having high conductivityand the first functional layer 1311 provided on the lower surface of thebase metal layer 1312 so as to have the function of improvinginterfacial bonding properties and the function of preventing hydrogendiffusion. The base metal layer 1312 may be formed of, for example, ametal having high conductivity, such as aluminum (Al), chromium (Cr),copper (Cu), titanium (Ti), molybdenum (Mo) or tungsten (W), or an alloyincluding at least one of these metals, and the first and secondfunctional layers 1311 and 1313 may be formed of a metal or atransparent metal, which may have a function of collecting hydrogen, oran alloy including at least one of these metals, such as MoTi, Ti orITO.

Thereafter, after the first layer 140 a and the second layer 150 havingdifferent ratios of oxygen and nitrogen are sequentially deposited, anopen region P1 is formed by selectively removing the first layer 140 aand the second layer 150 with a mask (not shown) having a first opening(corresponding to the open region P1). FIG. 4A exemplarily illustrateswet etching, and a relatively larger area of an upper portion having alarger contact area with a wet etchant is removed and a relativelysmaller area of a lower portion is removed. That is, the second layer150 and the first layer 140 a are removed such that the removed portionsthereof form a side wall having a regular tapered shape from the upperportion of the second layer 150 to the lower portion of the first layer140 a. In this case, a second open region 150H formed at the lowerportion of the second layer 150 may be greater in size than the openregion P1 formed at the lower portion of the first layer 140 a.

FIG. 4A illustrates merely one example, and as another example, when theopen regions of the first and second layers 140 a and 150 are formedusing dry etching, the first layer 140 a and the second layer 150 mayhave open regions P1 and 150H having the same width. In this case, theopen region P1 of the first layer 140 a and the second open region 150Hof the second layer 150 may have the same size.

Thereafter, the organic insulating film 160 may be formed of an organicmaterial, such as photoacryl or benzocyclobutene (BCB), on the secondlayer 150 so as to planarize the surface of the second layer 150, andthe hole 160H having a greater size than the open region 150H of thesecond layer 150 above the extension 130 a of the auxiliary wiring 130may be formed through the organic insulating film 160 by patterning theorganic insulating film 160. In the display device having transmissionparts T, when the hole 160H of the organic insulating film 160 isformed, the organic insulating film 160 may be removed from regionscorresponding to the transmission parts T, thereby being capable ofincreasing transmittance of the transmission parts T.

As shown in FIGS. 1 and 2, the first electrode 145 is formed bysequentially depositing the first transparent electrode layer 1411, thereflective metal layer 1412 and the second transparent electrode layer1413 on the organic insulating film 160 and then selectively removingthese layers 1411, 1412 and 1413. The first electrode 145 is formed tohave a slightly larger size than the emission part E, and thus, upwardreflection of light from the emission part E through the first electrode145 may be effectively performed, and the first electrode 145 may beconnected to the thin film transistor through the first connection partCT1 outside the emission part E.

As shown in FIG. 4B, the bank 170 having the first holes 170H1corresponding to the extensions 130 a, the second holes 170H2corresponding to the emission parts E, and the third holes 170H3corresponding to the transmission parts T is formed by applying a bankmaterial to the surface of the organic insulating film 160 andselectively removing the bank material.

As shown in FIG. 4C, in order to selectively remove the first layer 140a, a photoresist pattern 175 configured to shield one side of each ofthe first and second layers 140 and 150 and to have an open region P2 toopen the remaining side of each of the first and second layers 140 and150 is formed. One side of the photoresist pattern 175 configured toshield one side of each of the first and second layers 140 and 150extends to the extension 130 a of the auxiliary wiring 130, and theother side of the photoresist pattern 175 extends to the second layer150 so as to open a part of the upper surface of the second layer 150and the side parts of the first and second layers 140 and 150. The openregion P2 of the photoresist pattern 175 may be located at a positionwhich is shifted laterally from the open region P1 of the first layer140 formed in the process shown in FIG. 4A by about the length a of theundercut UC.

Thereafter, in the state in which the photoresist pattern 175 isprepared, as shown in FIG. 4D, the undercut UC is formed by removing theexposed side part of the first layer 140 using an etchant or etching gashaving no etching reactivity to the material of the second layer 150 andhaving etching reactivity to the material of the first layer 140. Here,the second layer 150 has no reactivity to the etchant or the etching gaswhen the first layer 140 is selectively etched, thus being capable ofmaintaining the open region 150H, as shown in FIG. 4A. On the otherhand, the exposed side part of the first layer 140 is removed with theetchant or the etching gas, and thus, the first layer 140 is removedmore than the second layer 150 by the designated width a, thereby beingcapable of defining the undercut UC.

As such, the first layer 140, in which the undercut UC is defined, andthe second layer 150 are referred to as the passivation structure 1400.

Thereafter, as shown in FIG. 4E, the organic layer 180 and the secondelectrode 190 are sequentially formed. Even though the organic layer 180is formed without using a fine metal mask, the organic layer 180 may bedisconnected in the undercut region by the first layer 140 and thesecond layer 150 having the open regions 140H and 150H having a sizedifference. That is, because the second layer 150 protrudes more thanthe first layer 140 having the undercut, the second layer 150 serves asa shade when the organic layer 180 is deposited, and may prevent theorganic layer 180 from being deposited on a region of the extension 130a, in which the first layer 140 is removed, below the second layer 150.The second electrode 190 includes a metal material, such as indium, zincor titanium, has excellent step coverage compared to the organic layer180, and may thus be deposited so as to enter into the undercut region.Thereby, after deposition of the second electrode 190, the secondelectrode 190 may be connected to the extension 130 a of the auxiliarywiring 130.

After formation of the second electrode 190, the capping layer (notshown) may be further formed on the second electrode 190.

The first electrode 145, the organic layer 180 and the second electrode190 formed in the emission part form the light emitting device OLED.

Thereafter, as shown in FIG. 4F, the encapsulation layer structure 300is formed by sequentially forming the first inorganic encapsulationlayer 310, the organic encapsulation layer 320 and the second inorganicencapsulation layer 330 on the second electrode 190.

As such, in the method for manufacturing the display device according toone aspect of the present disclosure, the passivation structure 1400protecting the thin film transistors includes a plurality of layers, theundercut structure UC, in which the first open region 140H of the firstlayer 140 of the passivation structure 1400 is greater in size than thesecond open region 150H of the second layer 150, is provided so as tocorrespond to the extension 130 a of the auxiliary wiring 130, theorganic layer 180 is disconnected at the undercut structure, andthereby, the second electrode 190 may be directly connected to theextension 130 a of the auxiliary wiring 130, and changes in thecharacteristics of the thin film transistors may be prevented due to themultilayer passivation structure 1400.

Hereinafter, compared to the above-described undercut structure in thepassivation structure of the display device according to the presentdisclosure, Test Example 1, in which a first electrode dummy pattern isformed of the same metal in the same layer as a first electrodeincluding a reflective electrode and an undercut is formed due to awidth difference between the first electrode dummy pattern and anovercoat layer provided thereunder, will be examined.

FIG. 5A is an SEM image of a display device to which an undercutstructure according to Test Example 1 is applied.

In Test Example 1, as shown in FIG. 5A, when the first electrode (anode)dummy pattern includes silver (Ag) having high reflectance, such as anAg alloy, because the undercut structure is formed between the firstelectrode dummy pattern and the overcoat layer by protruding the firstelectrode dummy pattern more than the overcoat layer OC providedthereunder, silver (Ag) having high reflectance in the protruding firstelectrode dummy pattern is oxidized, and thus rises and swells, andcauses deformation of the shapes of an organic layer EL and a cathode,which are subsequently formed thereon, thereby causing a connectionfailure between an auxiliary wiring S/D and the cathode, i.e., a secondelectrode.

In a display device including transmission parts, because the area ofemission parts is reduced due to presence of the transmission parts, ina situation in which the respective emission parts require highefficiency and essentially require use of highly reflective metal, whenthe dummy pattern of a first electrode (anode) including a highlyreflective metal has a protruding tip, swelling of the highly reflectivefirst electrode dummy pattern in the subsequent process may occur as inTest Example 1 shown in FIG. 5A. Therefore, the inventors of the presentdisclosure propose a method which the side part of the first electrode145 is protected by the bank 170, and an undercut part (void part) isformed by changing a different layer from the first electrode 145,particularly the passivation structure 1400.

Thereby, exposure of the side part of the auxiliary connection patternincluding the reflective metal layer to the outside is prevented,deformation of the first electrode using the reflective metal isprevented, and thereby, a reliable connection structure between theauxiliary wiring and the second electrode may be realized.

FIG. 5B is a photograph representing mura occurring on the surface of adisplay device to which a single passivation film according to TestExample 2 is applied.

FIG. 5B is a photograph representing, when the display device includesthin film transistors including an oxide semiconductor layer accordingto Test Example 2, the surface of the display device after formation ofa passivation film using a single silicon oxide (SiO_(x)) film. However,the passivation film using the oxide film may block hydrogen generatedfrom the inside of a thin film transistor array but, when anencapsulation layer structure is formed on light emitting devicesprovided above the thin film transistors by a low-temperature process,the densities of inorganic encapsulation layers included in theencapsulation layer structure are low and thus hydrogen ion contents inthe inorganic encapsulation layers are high, and hydrogen ions in theinorganic encapsulation layers may migrate towards elements under theencapsulation layer structure in the display device according to TestExample 2. FIG. 5B illustrates that the hydrogen ions generated from theinorganic encapsulation layers migrate to the thin film transistorsprovided therebelow and impart conductivity to the channels of the thinfilm transistors, and thus cause mura on the surface of the displaydevice.

Recently, display devices are gradually developed to satisfy therequirements of slimness and flexibility, and for this purpose, thesubstrate 100 is formed of a flexible material and the thicknesses ofelements provided on the substrate 100 tend to be reduced. Therefore, anencapsulation substrate disposed opposite the substrate 100 is omitted,and the encapsulation layer structure 300 including the inorganicencapsulation layers 310 and 330 and the organic encapsulation layer320, which are alternately stacked, as described above, may be formed soas to protect the light emitting devices from ambient air and to preventmoisture penetration thereinto.

Further, in the display device, in order to prevent deformation of theflexible substrate 100 due to heat applied during a thin film transistorarray formation process, instead of polysilicon requiring ahigh-temperature process executed at a high temperature equal to orhigher than 400° C., the semiconductor layer (active layer) may beformed of an oxide semiconductor manufactured at a temperature lowerthan the above temperature.

The oxide semiconductor is formed of an oxide film including at leastone of indium (In), gallium (Ga) or zinc (Zn), when polarized ions, suchas hydrogen ions, enter into a channel formed in the oxidesemiconductor, threshold voltage characteristics are drasticallychanged, and in order to prevent such change, the passivation filmhaving the function of preventing hydrogen diffusion is formed.

FIG. 6 is a graph representing negative bias thermal stress (NBTS)characteristics at a high temperature of the display device according toTest Example 2 and a display device according to Test Example 3.

In Test Example 2, the single passivation film is used to protect thethin film transistors, and in Test Example 3, a two-layer passivationstructure including a first layer and a second layer is used to protectthin film transistors, as shown in FIGS. 1 to 3. Elements other than thepassivation film in Test Example 2 and Test Example 3 are the same.

In order to examine negative bias thermal stress (NBTS) characteristics,after formation of an encapsulation layer structure of a display device,change in the threshold voltage of thin film transistors under severeconditions of a temperature of about 110° C. is observed. Here,inorganic encapsulation layers of the encapsulation layer structure arenitride films formed at a low temperature.

In Test Example 3, the two-layer passivation structure including thefirst layer and the second layer is applied, like the display deviceaccording to one aspect of the present disclosure described withreference to FIGS. 1 to 3, the first layer is formed of a silicon oxide(SiO_(x)) film, and the second layer is formed of a silicon nitride(SiN_(x)) film. Both the first and the second films are formed at a hightemperature equal to or higher than 200° C., source electrodes and drainelectrodes of the thin film transistors directly contact the firstlayer, and the first layer has a greater thickness than the thickness ofthe second layer.

In Test example 2, the single passivation film is formed of a singleoxide film.

In the NBTS test, a threshold voltage shift of −14 V occurred in thedisplay device according to Test example 2 after 10⁵ seconds elapse, anda threshold voltage shift of −4 V occurred in the display deviceaccording to Test example 3 after 10⁵ seconds elapse, and thereby, itmay be confirmed that, when the multilayer passivation film is applied,changes in the characteristics of the thin film transistors may begreatly prevented due to prevention of hydrogen diffusion. Themultilayer passivation film of Test Example 3, which further includesthe second layer having a smaller thickness than that of the first layerand a different composition ratio of oxygen and nitrogen from that ofthe first layer, may reduce change in threshold voltage to half or morecompared to the structure having the single passivation film formed ofthe same material as the multilayer passivation film and having athickness corresponding to the sum of the thickness of the first layerand the thickness of the second layer.

Further, a threshold voltage shift of −4 V occurred in the displaydevice according to Test example 2 after 10⁴ seconds elapse, but athreshold voltage shift of −4 V occurred in the display device accordingto Test example 3 after 10⁵ seconds elapse, and thereby, it may beconfirmed that the display device according to Test example 3 hasstability over time.

FIG. 7 is a longitudinal-sectional view illustrating the evaluatedstructure of an undercut of a multilayer passivation structure accordingto Test Example 4, and FIG. 8 is an SEM image representing themultilayer passivation structure according to Test Example 4 shown inFIG. 7 after dry etching.

Test Example 4 shown in FIG. 7 represents a target structure in which anoxide film and a nitride film having different components have openregions having different widths.

In the target structure of Test Example 4, a separation film 420 isformed on a base film 410, a first oxide film 431, a first nitride film441, a second nitride film 442 and a second oxide film 431 aresequentially formed thereon, the first oxide film 431, the first nitridefilm 441, the second nitride film 442 and the second oxide film 431 areprimarily removed by the same width under first conditions, and then,the first and second nitride films 441 and 442 formed of a nitride filmcomponent are secondarily more removed under second conditions so as tohave a different width from the first and second oxide films 431 and432.

For example, sulfur hexafluoride (SF₆) and argon (Ar) were used in aratio of 1:3 (SF₆:Ar) as etching gases under the first conditions, andsulfur hexafluoride (SF₆) and argon (Ar) were used in a ratio of 3:1(SF₆:Ar) as etching gases under the second conditions.

After dry etching was completed using the etching gases at differentratios of SF₆:Ar, it may be confirmed from FIG. 8, illustrating anetched state on the separation film 420, that the first and secondnitride films 441 and 442 are removed more than the first and secondoxide films 431 and 432. In a layer structure including films havingdifferent composition ratios, such as an oxide film and a nitride film,the two films may be patterned so as to have open regions having thesame width or similar widths, and thereafter, the lower film among thetwo films may be selectively more removed by reaction gases or anetchant having reactivity to the lower film. In this case, as shown inFIG. 8, it may be confirmed that, even if some parts of the first andsecond nitride films 441 and 442 are removed, an undercut having aheight h and a length a is formed between the second oxide films 432remaining on the first and second nitride films 441 and 442 and thefirst and second nitride films 441 and 442. The height h corresponds tothe sum of the thickness of the first nitride film 441 and the thicknessof the second nitride film 442, and the thickness required by theundercut may be adjusted by controlling the deposition thicknesses ofthe first and second nitride films 441 and 442. The length a may beadjusted within the range of about 0.4 μm to 2 μm.

Test Example 4 shown in FIGS. 7 and 8 is merely one example, and filmsconfigured to be relatively more etched by varying etching gases or anetchant may be oxide films and a film configured to protrude on theoxide films may be a nitride film.

Through Test Example 4, it may be confirmed that an undercut structuremay be secured in a stack of inorganic films having differentcomposition ratios.

Hereinafter, a display device according to another aspect of the presentdisclosure will be described.

FIG. 9 is a longitudinal-sectional view illustrating the display deviceaccording to another aspect of the present disclosure.

As shown in FIG. 9, the display device according to another aspect ofthe present disclosure may include a substrate 200 having emission partsE, transmission parts T and auxiliary connection parts CTA, auxiliarywirings 230 provided in the auxiliary connection parts CTA of thesubstrate 200, a passivation structure 2400 formed by stacking a firstlayer 240 and a second layer 250 and configured such that an open regionof the first layer 240 is greater in size than an open region of thesecond layer 250 with respect to the auxiliary wiring 230, a bank 270provided on the passivation structure 2400 and configured to have holes,which is greater in size than the open region of the first layer 240,corresponding to the auxiliary connection parts CTA, and holesrespectively corresponding to the emission parts E and the transmissionparts T, and light emitting devices OLED respectively provided inemission parts E, each of the light emitting devices OLED including afirst electrode 255 including a reflective metal layer 2511, an organiclayer 280 including at least one emission layer, and a second electrode290, and the second electrode 290 may be directly connected to theauxiliary wiring 230 in the open region of the first layer 240 under thesecond layer 250.

FIG. 9 illustrates a non-active area NA including pad electrodes 238,and an active area AA including storage capacitor regions Cst, theemission parts E, the transmission parts T and the auxiliary connectionparts CTA. A detailed description of some parts in this aspect, whichare substantially the same as those in the aspect described above withreference to FIGS. 1 to 3, will be omitted, and elements, which areadditionally provided in this aspect, will be described in detail.

A light-shielding layer 211 may be provided on the substrate 200 so asto block light from the lower part of an oxide semiconductor layer 214,and light-shielding patterns 210 and 213 may be formed in the same layeras the light-shielding layer 211. The light-shielding patterns 210 and213 may function as lines configured to apply voltage to the auxiliarywiring 230 and a first storage electrode 235, respectively.

A buffer layer (not shown) may be further formed between the substrate200 and the light-shielding patterns 210 and 213 and the light-shieldinglayer 211 so as to prevent impurities of the substrate 200 frompenetrating into a thin film transistor array provided thereon.

The light-shielding patterns 210 and 213 and the light-shielding layer211 may include a first metal layer 2111 and a second metal layer 2112,as shown in this figure. However, the light-shielding patterns 210 and213 and the light-shielding layer 211 are not limited thereto, and maybe formed as a single layer or include a plurality of layers. The firstand second metal layers 2111 and 2112 may be formed of a metal havinghigh conductivity, such as aluminum (Al), chromium (Cr), copper (Cu),titanium (Ti), molybdenum (Mo) or tungsten (W), or an alloy including atleast one of these metals. Particularly, when the first and second metallayers 2111 and 2112 are formed of a metal or a metal alloy which maycollect hydrogen, such as MoTi, the first and second metal layers 2111and 2112 may prevent deformation of the oxide semiconductor layer 214due to hydrogen included in the substrate 200 or a first interlayerinsulating film 205.

The first interlayer insulating film 205 may be formed so as to coverthe light-shielding patterns 210 and 213 and the light-shielding layer211.

Further, the oxide semiconductor layer 214 may be formed on the firstinterlayer insulating film 205 so as to overlap the light-shieldinglayer 211. Here, the oxide semiconductor layer 214 may be formed as adifferent semiconductor, such as polysilicon or the like. When the oxidesemiconductor layer 214 is formed and the passivation structure 2400according to the present disclosure is applied, changes in thecharacteristics of the oxide semiconductor layer 214 may be moreeffectively prevented.

Each of thin film transistors TFT includes the oxide semiconductor layer214, a gate electrode 227 configured to overlap the channel of thesemiconductor layer 214 with a gate insulating film 209 interposedtherebetween, and a source electrode 232 and a drain electrode 234spaced apart from the gate electrode 227 and connected to both sides ofthe semiconductor layer 214.

A second storage electrode 229 may be formed in the same layer as thegate electrode 227 in the storage capacitor region Cst, and an auxiliaryconnection pattern 225 may be formed in the auxiliary connection partCTA. The auxiliary connection pattern 225 may be omitted.

The gate electrode 227, the second storage electrode 229 and theauxiliary connection pattern 225 may include a third metal layers 2211and a fourth metal layer 2212, as shown in this figure. However, thegate electrode 227, the second storage electrode 229 and the auxiliaryconnection pattern 225 are not limited thereto, and may be formed as asingle layer or include a plurality of layers. The third and fourthmetal layers 2211 and 2212 may be formed of a metal having highconductivity, such as aluminum (Al), chromium (Cr), copper (Cu),titanium (Ti), molybdenum (Mo) or tungsten (W), or an alloy including atleast one of these metals. Particularly, when the third and fourth metallayers 2211 and 2212 are formed of a metal or a metal alloy which maycollect hydrogen, such as MoTi, the third and fourth metal layers 2211and 2212 may prevent deformation of the oxide semiconductor layer 214due to hydrogen generated from the inside of the device or migratingfrom other layers.

A second interlayer insulating film 220 is formed so as to cover thegate electrode 227, the second storage electrode 229 and the auxiliaryconnection pattern 225.

The auxiliary wiring 230, the source electrode 232, the drain electrode234 and the first storage electrode 235 are formed on the secondinterlayer insulating film 220. In the same process, the pad electrodes238 may be formed in the non-active area NA.

One side of each of the first storage electrode 235 and the auxiliarywiring 230 may be connected to a corresponding one of thelight-shielding patterns 213 and 210 by through holes formed through thefirst and second interlayer insulating films 205 and 220. A connectionhole may be formed by selectively removing the second interlayerinsulating film 220 so as to expose a part of the auxiliary connectionpattern 225, thus being capable of connecting the auxiliary connectionpattern 225 to the auxiliary wiring 230.

The pad electrodes 238, the auxiliary wiring 230, the source electrode232, the drain electrode 234 and the first storage electrode 235 mayinclude a fifth metal layer 2311 and a sixth metal layer 2312. However,the pad electrodes 238, the auxiliary wirings 230, the source electrode232, the drain electrode 234 and the first storage electrode 235 are notlimited thereto, and may be formed as a single layer or include aplurality of layers. Like the auxiliary wiring 130 shown in FIGS. 2 and3, the pad electrodes 238, the auxiliary wiring 230, the sourceelectrode 232, the drain electrode 234 and the first storage electrode235 may have a three-layer structure.

The fifth and sixth metal layers 2311 and 2312 may be formed of a metalhaving high conductivity, such as aluminum (Al), chromium (Cr), copper(Cu), titanium (Ti), molybdenum (Mo) or tungsten (W), or an alloyincluding at least one of these metals. Particularly, when the fifth andsixth metal layers 2311 and 2312 are formed of a metal or a metal alloywhich may collect hydrogen, such as MoTi, the fifth and sixth metallayers 2311 and 2312 may prevent deformation of the oxide semiconductorlayer 214 due to hydrogen generated from the inside of the device ormigrating from other layers.

The passivation structure 2400 is acquired by forming the first layer240 and the second layer 250 formed of at least different inorganicinsulating films on the pad electrodes 238, the auxiliary wiring 230,the source electrode 232, the drain electrode 234 and the first storageelectrode 235, and an undercut structure configured to expose a part ofthe auxiliary wiring 230 is formed by removing a partial width of thefirst layer 240 more than the second layer 250, as shown in FIG. 3.

An inorganic insulating film 260 for planarization is provided on thepassivation structure 2400 in the active area AA except for theauxiliary connection parts CTS and the transmission parts T.

A connection hole (with reference to CT1 of FIG. 1) configured to exposea part of the drain electrode 234 is formed through the organicinsulating film 260, and the first electrode 255 formed, for example, bystacking a first transparent electrode layer 2512, the reflective metallayer 2511 and a second transparent electrode layer 2513, so as to havea greater size than the emission part E, is connected to the drainelectrode 234 through the connection hole CT1. Simultaneously withformation of the first electrode 255, pad protective electrodes 257 maybe formed on the pad electrodes 238. The pad protective electrodes 257may be formed of one or two of the metal layers 2512, 2511 and 2513 ofthe first electrode 255.

The bank 270 configured to open the emission parts E, the transmissionparts T and the auxiliary connection parts CTA is provided so as tocover the edge of the first electrode 255.

The organic layer 280 and the second electrode 290 are sequentiallyprovided on the bank 270, the emission parts E and the transmissionparts T.

The first electrode 255, the organic layer 280 and the second electrode290, which are sequentially stacked, form the light emitting deviceOLED.

The organic layer 280 and the second electrode 290 may be formed usingopen masks having an opening corresponding to at least the entirety ofthe active area AA without using fine metal masks having openingscorresponding to the respective emission parts. In this case, formationof the organic layer 280 in the region of the undercut UC of thepassivation film 2400 is constrained, and the second electrode 290 hasrelatively excellent step coverage compared to the organic layer 280,and may thus be connected to the auxiliary wiring 230 within theundercut UC. The opening of the open mask used to form the organic layer280 and the opening of the open mask used to form the second electrode290 may be different, and the opening of the open mask used to form thesecond electrode 290 may be greater than the opening of the open maskused to form the organic layer 280 so as to apply voltage to the secondelectrode 290 from the outside.

The encapsulation layer structure 300 may be formed on the lightemitting devices OLED, for example, by sequentially stacking a firstinorganic encapsulation layer 310, an organic encapsulation layer 320and a second inorganic encapsulation layer 330. The encapsulation layerstructure 300 may include two inorganic encapsulation layers and oneorganic encapsulation layer at the minimum, and may include a largernumber of encapsulation layers as long as inorganic encapsulation layersand organic encapsulation layers are alternately formed.

In order to prevent penetration of moisture from the outside, the firstand second inorganic encapsulation layers 310 and 330 may extend towardsthe non-active area NA compared to the organic encapsulation layer 320.

On the encapsulation layer structure 300, as shown in FIG. 9, a colorfilter layer 400 or a touch electrode array may be further provided. Inthis case, an encapsulation substrate disposed opposite the substrate200 may be omitted so as to reduce the total thickness of the displaydevice. The color filter layer 400 is formed so as to correspond to atleast the emission parts E except for the transmission parts T, and isformed of a pigment which transmits only the wavelengths of a color oflight, which a corresponding emission part E desires to display.Different color filter layers 400 may be applied to the emission parts Econfigured to emit light with different colors.

Hereinafter, a method for manufacturing the display device according toanother aspect of the present disclosure will be described.

FIGS. 10A to 10F are longitudinal-sectional views illustrating themethod for manufacturing the display device according to another aspectof the present disclosure.

As shown in FIG. 10A, the light-shielding layer 211 may be formed on thesubstrate 200, and in this case, the light-shielding patterns 210 and213 may be formed in the same layer as the light-shielding layer 211.The buffer layer (not shown) may be formed between the substrate 200 andthe light-shielding patterns 210 and 213 and the light-shielding layer211 so as to prevent impurities of the substrate 200 from penetratinginto the thin film transistor array provided thereon.

The light-shielding patterns 210 and 213 and the light-shielding layer211 may include the first metal layer 2111 and the second metal layer2112, as shown in these figures. However, the light-shielding patterns210 and 213 and the light-shielding layer 211 are not limited thereto,and may be formed as a single layer or include a plurality of layers.The first and second metal layers 2111 and 2112 may be formed of a metalhaving high conductivity, such as aluminum (Al), chromium (Cr), copper(Cu), titanium (Ti), molybdenum (Mo) or tungsten (W), or an alloyincluding at least one of these metals.

The first interlayer insulating film 205 may be formed so as to coverthe light-shielding patterns 210 and 213 and the light-shielding layer211.

Further, the oxide semiconductor layer 214 may be formed on the firstinterlayer insulating film 205 so as to overlap the light-shieldinglayer 211.

The gate electrode 227 is formed to overlap the channel of thesemiconductor layer 214 with the gate insulating film 209 interposedtherebetween, the second storage electrode 229 may be formed in the samelayer as the gate electrode 227 in the storage capacitor region Cst, andthe auxiliary connection pattern 225 may be formed in the auxiliaryconnection part CTA. The auxiliary connection pattern 225 may beomitted. In the same process, gate lines may be formed.

Thereafter, the second interlayer insulating film 220 may be formed soas to cover the gate electrode 227, the second storage electrode 229 andthe auxiliary connection pattern 225.

Thereafter, through holes are formed through the first and secondinterlayer insulating films 205 and 220 so as to expose a part of eachof the light-shielding patterns 210 and 213, and connection holes areformed through the second interlayer insulating film 220 so as to exposeboth sides of the oxide semiconductor layer 214 and a part of theauxiliary connection pattern 225.

The first storage electrode 235 connected to the light-shielding pattern213 in the storage capacitor region Cst, the source electrode 232 andthe drain electrode 234 connected to both sides of the oxidesemiconductor layer 214, and the auxiliary wiring 230 having both sidesconnected to the light-shielding pattern 210 may be formed by stackingthe fifth metal layer 2311 and the sixth metal layer 2312 on the secondinterlayer insulating film 220 so as to fill the respective throughholes and connection holes and then selectively removing the fifth andsixth metal layers 2311 and 2312. In the same process, data lines may beformed and the pad electrodes 238 may be formed in the non-active areaNA.

Thereafter, after the first layer 240 a and the second layer 250 havingdifferent ratios of oxygen and nitrogen are sequentially deposited, boththe first layer 240 a and the second layer 250 are patterned using amask (not shown) having openings corresponding to a portion of a flatpart of the auxiliary wiring 230, a part of the drain electrode 234, thepad electrodes 238 and the transmission parts T. Etching gases or anetchant applied to such patterning have the same reactivity or similarreactivities to the first layer 240 a and the second layer 250, andthus, the first layer 240 a and the second layer 250 are patterned so asto have open regions having the same width or similar widths, the sideparts of the open regions of the first layer 240 a and the second layer250 form a tapered shape but there may be no width difference at theinterface between the first layer 240 a and the second layer 250.

Here, the transmittance of the transmission parts T may be improved byremoving the first layer 240 a and the second layer 250 from thetransmission parts T.

Thereafter, the organic insulating film 260 may be formed by depositingan organic insulating film material on the upper surface of the secondlayer 250, and may then be patterned so as to have the first connectionpart CT1 corresponding to the drain electrode 234 and a hole 260Hcorresponding to the auxiliary wiring 230 and to be removed from thetransmission parts T.

As shown in FIG. 10B, the first electrode 255 is formed by sequentiallydepositing the first transparent electrode layer 2512, the reflectivemetal layer 2511 and the second transparent electrode layer 2513 on theorganic insulating film 260 and then selectively removing these layers2512, 2511 and 2513. The first electrode 255 is formed to have aslightly larger size than the emission part E, and thus, upwardreflection of light from the emission part E through the first electrode255 may be effectively performed, and the first electrode 255 may beconnected to the drain electrode 234 of the thin film transistor throughthe first connection part CT1 in the organic insulating film 260 outsidethe emission part E.

Thereafter, the bank 270 having the holes corresponding to the auxiliarywirings 230, the transmission parts T and the emission parts E is formedby applying a bank material to the surface of the organic insulatingfilm 260 and selectively removing the bank material.

Thereafter, as shown in FIG. 10C, a photoresist pattern 275 is formed soas to expose one side part of the first layer 240 on the auxiliarywiring 230 on the substrate 200 and to cover the other side part of thefirst layer 240 on the auxiliary wiring 230.

Thereafter, the side part of the first layer 240 exposed from thephotoresist pattern 275 is removed compared to the second layer 250,thus forming the undercut UC, as shown in FIG. 10D. Thereafter, thephotoresist pattern 275 is removed.

The first layer 240 and the second layer 250 having a width differencebetween the open regions thereof through the process of FIG. 10D arereferred to as the passivation structure (with reference 2400 of FIG.10F).

Thereafter, as shown in FIG. 10E, the organic layer 280 and the secondelectrode 290 are formed.

The organic layer 280 may be disconnected at the region of the undercutUC due to the first layer 240 and the second layer 250 having the widthdifference between the open regions thereof without using a fine metalmask. That is, the second layer 250 on the undercut UC protrudes morethan the first layer 140, and serves as a shade when the organic layer280 is deposited, and may prevent the organic layer 280 from beingdeposited on the region, in which the first layer 240 is removed, belowthe second layer 250. The second electrode 290 includes a metalmaterial, such as indium, zinc or titanium, has excellent step coveragecompared to the organic layer 280, and may thus be deposited so as toenter into the undercut region. Thereby, after deposition of the secondelectrode 290, the second electrode 290 may be connected to theauxiliary wiring 230.

The organic layer 280 and the second electrode 290 may be formed usingopen masks having an opening corresponding to the entirety of the activearea AA without using fine metal masks having openings corresponding tothe respective emission parts E. In this case, formation of the organiclayer 280 in the region of the undercut UC of the passivation film 2400is constrained, and the second electrode 290 has relatively excellentstep coverage compared to the organic layer 280, and may thus beconnected to the auxiliary wiring 230 within the undercut UC. Theopening of the open mask used to form the organic layer 280 and theopening of the open mask used to form the second electrode 290 may bedifferent, and the opening of the open mask used to form the secondelectrode 290 may be greater than the opening of the open mask used toform the organic layer 280 so as to apply voltage to the secondelectrode 290 from the outside.

After formation of the second electrode 290, the capping layer (notshown) may be further formed on the second electrode 290.

The first electrode 255, the organic layer 280 and the second electrode290 formed in the emission part form the light emitting device OLED.

As shown in FIG. 10F, the encapsulation layer structure 300 is formed bysequentially forming the first inorganic encapsulation layer 310, theorganic encapsulation layer 320 and the second inorganic encapsulationlayer 330 on the second electrode 290.

The encapsulation layer structure 300 may be formed on the lightemitting devices OLED, for example, by sequentially stacking the firstinorganic encapsulation layer 310, the organic encapsulation layer 320and the second inorganic encapsulation layer 330 in order. Theencapsulation layer structure 300 may include two inorganicencapsulation layers and one organic encapsulation layer at the minimum,and may include a larger number of encapsulation layers as long asinorganic encapsulation layers and organic encapsulation layers arealternately formed.

In order to prevent penetration of moisture from the outside, the firstand second inorganic encapsulation layers 310 and 330 may extend towardsthe non-active area NA compared to the organic encapsulation layer 320.

The color filter layer 400 or a touch electrode array may be furtherprovided on the encapsulation layer structure 300. In this case, anencapsulation substrate disposed opposite the substrate 200 may beomitted so as to reduce the total thickness of the display device. Thecolor filter layer 400 is formed so as to correspond to at least theemission parts E except for the transmission parts T, and is formed of apigment which transmits only the wavelengths of a color of light, whicha corresponding emission part E desires to display. Different colorfilter layers 400 may be applied to the emission parts E configured toemit light with different colors.

As such, in the method for manufacturing the display device according toanother aspect of the present disclosure, the passivation structure 2400protecting the thin film transistors includes a plurality of layers, theundercut structure UC, in which the open region of the first layer 240of the passivation structure 2400 is greater in size than the openregion of the second layer 250, is provided so as to correspond to theauxiliary wiring 230, the organic layer 280 is disconnected in theundercut structure, and thereby, the second electrode 290 may bedirectly connected to the auxiliary wiring 230, and changes in thecharacteristics of the thin film transistors may be prevented due to themultilayer passivation structure 2400.

FIG. 11 is an SEM image of an undercut structure according to TestExample 5, i.e., the undercut structure of the display device accordingto the present disclosure.

FIG. 11 shows an undercut according to Test Example 5 formed by etchinga first layer more than a second layer formed on an auxiliary wiring,like the auxiliary connection parts show in FIGS. 3 and 9. That is, itmay be confirmed that, when the first layer and the second layer areformed of different materials and thus etch rates thereof are different,the undercut may be formed in the first layer without collapsing thesecond layer.

As is apparent from the above description, a display device according tothe present disclosure has the following effects.

First, in the display device according to the present disclosure, apassivation structure protecting thin film transistors includes aplurality of layers, an undercut structure, in which the open region ofa first layer of the passivation structure is greater in size than theopen region of a second layer of the passivation structure, is providedso as to correspond to a part of an auxiliary wiring or an extension ofthe auxiliary wiring, an organic layer is disconnected at the undercutstructure, and thereby, a second electrode, which is subsequentlyformed, may be directly connected to the auxiliary wiring, and changesin the characteristics of the thin film transistors may be prevented dueto the multilayer passivation structure.

Second, the multilayer passivation structure may prevent penetration ofhydrogen from the inside of an encapsulation layer structure ordiffusion of hydrogen into a thin film transistor array without changingthe thickness of a metal layer forming thin film transistors, and thus aprocess for defining an undercut is applied to the passivation structurewithout adding a mask, thereby being capable of preventing change in thethreshold voltage of the thin film transistors or changes in othercharacteristics. Therefore, deterioration of yield may be prevented.

Third, in a structure in which emission parts having a small area due toprovision of transmission parts use a highly reflective metal in orderto increase luminous efficacy, exposure of the highly reflective metalat a connection part with the auxiliary wiring is prevented, therebybeing capable of improving reliability of the device while preventingchange in the highly reflective metal.

Fourth, when the display device requires slimness and flexibility and athinned encapsulation layer structure is applied, the multilayerpassivation structure formed on the thin film transistor array blocksmigration of hydrogen from the encapsulation layer structure formed by alow-temperature process, thereby being capable of minimizing change inthe threshold voltage of the thin film transistors and securingstability of light emitting devices over time.

For realizing the above effects, a display device according to oneaspect of the disclosure can comprise an auxiliary wiring on asubstrate, a passivation structure including a first layer and a secondlayer stacked on the auxiliary wirings, wherein an open region of thefirst layer is greater than an open region of the second layer withrespect to the auxiliary wiring, a bank on the passivation structure,the bank to have a first hole greater than the open region of the firstlayer corresponding to the auxiliary wiring, and a second holecorresponding to an emission part and a light emitting device at theemission part, each of the light emitting devices comprising a firstelectrode comprising a reflective metal layer, an organic layercomprising at least one emission layer, and a second electrode, whereinthe second electrode extends towards the auxiliary wiring inside thesecond hole of the bank and is directly connected to the auxiliarywiring in the open region of the first layer under the second layer.

The first and second layers may be inorganic films, and have differentcontent ratios of oxygen and nitrogen.

One of the first and second layers may be an oxide film, and a remainingone of the first and second layers may be a nitride film.

A thickness of the first layer may be greater than a sum of a thicknessof the organic layer and a thickness of the second electrode of thelight emitting device.

The open region of the first layer may be greater than the open regionof the second layer by a width of 0.4 μm to 2 μm.

The auxiliary wiring may be provided in the same layer as one electrodeof a thin film transistor connected to the first electrode of the lightemitting device. The passivation structure may cover the thin filmtransistor.

The thin film transistor may comprise an oxide semiconductor layer, agate electrode to overlap a part of the oxide semiconductor layer, and asource electrode and a drain electrode connected to both ends of theoxide semiconductor layer. The gate electrode, the source electrode andthe drain electrode may comprise a plurality of metal layers, and atleast one of the metal layers comprises a metal or a metal alloy capableof collecting hydrogen.

The first electrode may have a stack structure comprising a firsttransparent conductive layer, the reflective metal layer and a secondtransparent conductive layer. And the first transparent conductive layermay be bonded to the drain electrode of the thin film transistor bycladding.

The display device according to one aspect of the disclosure may furthercomprise a light-shielding layer under the oxide semiconductor layer andcomprising a metal layer capable of collecting hydrogen. At least oneconnection pattern connected to the auxiliary wiring may be furtherprovided in the same layer as the light-shielding layer.

The display device according to one aspect of the disclosure may furthercomprise an encapsulation layer structure to cover the light emittingdevices. The encapsulation layer structure may comprise at least oneorganic layer and inorganic layers to contact upper and lower surfacesof the at least one organic layer. And among the inorganic layers of theencapsulation layer structure, a lowermost inorganic layer may enterinto the first holes.

Among the first and second layers, a layer corresponding to a nitridefilm may have a higher density than a density of the lowermost inorganiclayer of the encapsulation layer structure.

The display device according to one aspect of the disclosure may furthercomprise an organic insulating layer between the passivation structureand the bank. The bank may further comprise a third hole. The organicinsulating layer and the passivation structure under the bank may have aremoval part corresponding to the third hole.

The display device according to another aspect of the disclosure maycomprise a substrate having an emission part, a transmission part and anauxiliary connection part, an auxiliary wiring at the auxiliaryconnection parts of the substrate, a passivation structure including afirst layer and a second layer stacked on the auxiliary wiring, the bankto have a first hole greater than the open region of the first layercorresponding to the auxiliary wiring, a second hole corresponding tothe emission part, and a third hole corresponding to the transmissionpart, and a light emitting device at the emission parts, the lightemitting devices comprising a first electrode comprising a reflectivemetal layer, an organic layer comprising at least one emission layer,and a second electrode.

An open region of the first layer may be greater than an open region ofthe second layer with respect to the auxiliary wiring, a bank on thepassivation structure. And the second electrode may extend towards theauxiliary wiring in the open region of the first layer under the secondlayer.

The first and second layers may be inorganic films, and may havedifferent content ratios of oxygen and nitrogen.

A thickness of the first layer may be greater than a sum of a thicknessof the organic layer and a thickness of the second electrode of each oflight emitting devices.

The display device according to another aspect of the disclosure mayfurther comprise an encapsulation layer structure configured to coverthe light emitting device. The encapsulation layer structure maycomprise at least one organic layer and inorganic layers to contactupper and lower surfaces of the at least one organic layer. And amongthe inorganic layers of the encapsulation layer structure, a lowermostinorganic layer may enter into the first hole.

The first layer and the second layer of the passivation structure mayhave higher densities than a density of the lowermost inorganic layer ofthe encapsulation layer structure.

The passivation structure may cover a thin film transistor. The thinfilm transistor may comprise an oxide semiconductor layer, a gateelectrode to overlap a part of the oxide semiconductor layer, and asource electrode and a drain electrode connected to both ends of theoxide semiconductor layer. The gate electrode, the source electrode andthe drain electrode may comprise a plurality of metal layers,respectively. And at least one of the metal layers may comprise a metalor a metal alloy capable of collecting hydrogen. The auxiliary wiringmay be connected to the source electrode and the drain electrode.

At least one layer of the passivation structure may be removed from thetransmission part.

The first electrode may have a stack structure comprising a firsttransparent conductive layer, the reflective metal layer and a secondtransparent conductive layer, and the first transparent conductive layermay be cladded to the drain electrode of the thin film transistor.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present disclosurewithout departing from the spirit or scope of the disclosure. Thus, itis intended that the present disclosure cover the modifications andvariations of this disclosure provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A display device comprising: an auxiliary wiring disposed on a substrate; a passivation structure including a first layer and a second layer stacked on the auxiliary wirings, wherein the first and second layer has open regions corresponding to the auxiliary wiring, and the open region of the first layer is greater than the open region of the second layer; a bank disposed on the passivation structure and having first and second holes corresponding to an emission part, wherein the first hole is greater than the open region of the first layer; and a light emitting device disposed at the emission part, each of the light emitting devices comprising a first electrode comprising a reflective metal layer, an organic layer comprising at least one emission layer, and a second electrode, wherein the second electrode extends towards the auxiliary wiring inside the second hole of the bank and is directly connected to the auxiliary wiring in the open region of the first layer under the second layer.
 2. The display device according to claim 1, wherein the first and second layers include inorganic films and have different ratios in oxygen and nitrogen.
 3. The display device according to claim 1, wherein one of the first and second layers is an oxide film and another one of the first and second layers is a nitride film.
 4. The display device according to claim 1, wherein a thickness of the first layer is greater than a sum of a thickness of the organic layer and a thickness of the second electrode of the light emitting device.
 5. The display device according to claim 1, wherein the open region of the first layer is greater than the open region of the second layer by a width of 0.4 μm to 2 μm.
 6. The display device according to claim 1, wherein the auxiliary wiring is provided in a same layer as one electrode of a thin film transistor connected to the first electrode of the light emitting device; and wherein the passivation structure covers the thin film transistor.
 7. The display device according to claim 1, wherein the thin film transistor comprises an oxide semiconductor layer, a gate electrode to overlap a part of the oxide semiconductor layer, and a source electrode and a drain electrode connected to both ends of the oxide semiconductor layer, and wherein the gate electrode, the source electrode and the drain electrode comprise a plurality of metal layers, and at least one of the metal layers comprises a metal or a metal alloy capable of collecting hydrogen.
 8. The display device according to claim 7, wherein the first electrode has a stack structure comprising a first transparent conductive layer, the reflective metal layer and a second transparent conductive layer, and the first transparent conductive layer is bonded to the drain electrode of the thin film transistor by cladding.
 9. The display device according to claim 7, further comprising a light-shielding layer under the oxide semiconductor layer and comprising a metal layer capable of collecting hydrogen, wherein at least one connection pattern connected to the auxiliary wiring is further provided in the same layer as the light-shielding layer.
 10. The display device according to claim 1, further comprising an encapsulation layer structure to cover the light emitting devices, wherein the encapsulation layer structure comprises at least one organic layer and inorganic layers to contact upper and lower surfaces of the at least one organic layer, and among the inorganic layers of the encapsulation layer structure, a lowermost inorganic layer enters into the first holes.
 11. The display device according to claim 10, wherein, among the first and second layers, a layer corresponding to a nitride film has a higher density than a density of the lowermost inorganic layer of the encapsulation layer structure.
 12. The display device according to claim 1, further comprising an organic insulating layer between the passivation structure and the bank, wherein the bank further comprises a third hole, and wherein the organic insulating layer and the passivation structure under the bank have a removal part corresponding to the third hole.
 13. A display device comprising: a substrate having an emission part, a transmission part and an auxiliary connection part; an auxiliary wiring at the auxiliary connection parts of the substrate; a passivation structure including a first layer and a second layer stacked on the auxiliary wiring, wherein an open region of the first layer is greater than an open region of the second layer with respect to the auxiliary wiring; a bank disposed on the passivation structure and having a first hole greater than the open region of the first layer corresponding to the auxiliary wiring, a second hole corresponding to the emission part, and a third hole corresponding to the transmission part; and a light emitting device disposed at the emission parts, the light emitting devices comprising a first electrode comprising a reflective metal layer, an organic layer comprising at least one emission layer, and a second electrode, wherein the second electrode extends towards the auxiliary wiring in the open region of the first layer under the second layer.
 14. The display device according to claim 13, wherein the first and second layers are inorganic films, and have different ratios in oxygen and nitrogen.
 15. The display device according to claim 13, wherein a thickness of the first layer is greater than a sum of a thickness of the organic layer and a thickness of the second electrode of each of light emitting devices.
 16. The display device according to claim 14, further comprising an encapsulation layer structure configured to cover the light emitting device, wherein the encapsulation layer structure comprises at least one organic layer and inorganic layers to contact upper and lower surfaces of the at least one organic layer, and among the inorganic layers of the encapsulation layer structure, a lowermost inorganic layer enters into the first hole.
 17. The display device according to claim 16, wherein the first layer and the second layer of the passivation structure have higher densities than a density of the lowermost inorganic layer of the encapsulation layer structure.
 18. The display device according to claim 13, wherein the passivation structure covers a thin film transistor that comprises an oxide semiconductor layer, a gate electrode to overlap with a part of the oxide semiconductor layer, and a source electrode and a drain electrode connected to both ends of the oxide semiconductor layer, wherein the gate electrode, the source electrode and the drain electrode comprise a plurality of metal layers, respectively, and at least one of the metal layers comprises a metal or a metal alloy capable of collecting hydrogen; and wherein the auxiliary wiring is connected to the source electrode and the drain electrode.
 19. The display device according to claim 13, wherein at least one layer of the passivation structure is removed from the transmission part.
 20. The display device according to claim 18, wherein the first electrode has a stack structure comprising a first transparent conductive layer, the reflective metal layer and a second transparent conductive layer, and the first transparent conductive layer is cladded to the drain electrode of the thin film transistor. 